I don't think just asserting that it's a failure waiting to happen is very helpful. If the Deadly++ encounter is a non starter, then that's a considering in talking about how to manage the form, not a reason not to do it.
Indeed. I think that is where the advice about having different stages to the fight, or reinforcements arriving in waves is useful: it lets the DM adjust on the fly in case of bad luck. You can still design an encounter that isn't too easy for the party, but change it partway through if the party get unlucky and are in trouble.
This is sort of an aside, but if there is inherent class imbalance with single nova encounters then there must be inherent class imbalance with multiple medium encounters. No one seems to talk much about that issue (that I have seen).
The multiple medium encounters are closer to what 5e is balanced around, so there isn't so much class imbalance. Generally a 6-8 encounter day, with two short rests and a long rest seems to be the sweet spot for class balance, backed up by comments from the designers to that end I believe.
Have 9+ encounters in a day and the game will start to favour at-will heavy classes like most martials. Have less than 5 encounters, and/or only one short rest, and the game starts to favour full-caster classes.
That's interesting. I never looked to see how many "points" (to use a term that really doesn't apply) the different classes had between rests. Does anyone know if the internet has produced a chart somewhere actually showing this information?
You can use the spell point variant to compare some classes. For example monks (particularly the 4-elements) are set up as short-rest-based half-casters. (As in they have about 1/3rd as many ki points as a half-caster would have spell points and spend them at the same costs as a half-caster would for the same spell.) Multiply their Ki by three (since it would be expected to refresh three times a day rather than once for a normal spell caster) and those are the resources the class is expected to have access to between long rests.
Likewise there is a rough equivalency if you convert Warlock spellcasting into spell points compared to a normal full caster: they have about 1/3rd as many.
So my experiences, with the various classes and NOVA capability (there will be holes, since my group heavily gravitates toward certain classes):
Artificer - A hole for me right of the bat (have seen exactly 1 artificer played in 5e, no one took one even in my Eberron campaign): But it's a half-caster with a lot of magic item related powers. Does not SEEM to be a big NOVA class, more of a long haul class. But, I'll leave specifics to someone more familiar.
Cleric - Full caster again. The big thing with the cleric going full bore every encounter? Healing word means, even IF someone drops, they won't stay dropped -and since the cleric isn't conserving slots this will just keep happening. Since it's got an ok range, the cleric can even do this from the back line. AND can do it and still attack from range (with a cantrip, but still). All the while they will have spirit guardians etc. to make enemies regret closing. If you have a twilight or a peace cleric and your group is only expecting the one encounter? at mid+ levels, you will not be able to keep a party member down without ludicrous damage and/or effects.
Rogue - No NOVA at all really other than a bit for the arcane trickster (and a tiny bit on the soulknife). But rogues are pretty solid, so should be able to hang in there. Plus, hopefully serious out of combat utility. Depending on what surrounds the one NOVA encounter, this class may end up being avoided.
Warlock - A "kind of" on the full caster. But because we're expecting only 1 encounter, their small spell output isn't nearly as limiting as it could be. Plus all their lower level spells being at "max" level will help a lot. Could excel here, with the right build. And certainly wouldn't be too far behind otherwise.
Thoughts?
Artificer: - You're correct. Artificers are very much built around sustained damage and support, and very little nova. In a long adventuring day they will excel but they cannot compete with a full caster in nova capability.
Cleric: - Healing word prevents casting another full spell that round. At a certain level it is probably more efficient to just continue to cast high-level spells rather than healing word and cantrip to get someone back up. Particularly if that character isn't a full caster and so may not be able to contribute as much as the cleric continuing to nova.
Warlock: - Will perform much worse than a long-rest-based full caster if the encounter goes on longer than their spell slots. A full-caster can just start casting their next lowest level of spells, but the warlock will be down to cantrips. (Very effective cantrips: better than a lot of martial attacks, but generally no competition between those and reasonably high level spells.)